''Kawasphenodon'' is an extinct genus of
sphenodontian
Rhynchocephalia (; ) is an order of lizard-like reptiles that includes only one living species, the tuatara (''Sphenodon punctatus'') of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a diverse g ...
reptile, known from the
Late Cretaceous
The Late Cretaceous (100.5â66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...
and
Paleocene
The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...
of
Patagonia in South America. The type species, ''K. expectatus'', was described in 2005 from jaw fragments found in late
Campanian aged sediments in the
Los Alamitos Formation, the jaw when complete was estimated to be 11 cm long, making it among the largest known sphenodontians. A second species, ''K. peligrensis'', around 1/3 the size of the type species, was described in 2014 also from jaw fragments in early
Paleocene
The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...
(
Danian
The Danian is the oldest age or lowest stage of the Paleocene Epoch or Series, of the Paleogene Period or System, and of the Cenozoic Era or Erathem. The beginning of the Danian (and the end of the preceding Maastrichtian) is at the Cretaceousâ ...
) sediments of the
Salamanca Formation, making it the youngest known definitive representative of Rhynchocephalia outside of New Zealand.
In the original description, it was found to be a member of
Sphenodontidae
Sphenodontidae is a family within the reptile group Rhynchocephalia, comprising taxa most closely related to the living tuatara of the genus ''Sphenodon''. Historically the taxa included within Sphenodontidae have varied greatly between analyses ...
, in other subsequent analyses it was found to be a member of
Opisthodontia. A 2020 analysis of rhyncocephalian relationships found it to be outside Opisthodontia, and instead a member of the Sphenodontinae as the closest known relative of the
tuatara
Tuatara (''Sphenodon punctatus'') are reptiles endemic to New Zealand. Despite their close resemblance to lizards, they are part of a distinct lineage, the order Rhynchocephalia. The name ''tuatara'' is derived from the MÄori language and m ...
, with an estimated divergence between the two genera in the Early Cretaceous.
Like most other rhynchocephalians, the teeth are
acrodont, with a deep
dentary, and it probably had an omnivorous habit.
References
{{Taxonbar, from=Q11737548
Sphenodontia
Cretaceous reptiles of South America
Paleocene reptiles of South America
Cretaceous Argentina
Paleogene Argentina
Fossils of Argentina
Tiupampan
Peligran
Campanian first appearances
Paleocene extinctions
Fossil taxa described in 2005
Golfo San Jorge Basin
Salamanca Formation